Cold Crystallization Behaviors of Poly(ethylene terephthalate)
Nori Yoshihara1,* Miaki Shibaya2 and Hideaki
Ishihara2
1 Toyobo Research Center, Toyobo Co., Ltd.
2-1, Katata, Otsu, Shiga, Japan 520-0292
TEL: 81-77-571-0083
FAX: 81-77-571-0084
e-mail: nori_yoshihara@kt.toyobo.co.jp
2 Advanced
Fibro-science, Kyoto Institute of Technology
Matsugasaki, Sakyo-ku,
Kyoto, Japan 606-8585
TEL:81-75-724-7365
FAX:81-75-724-7366
e-mail:h-ishi@ipc.kit.ac.jp
Cold crystallization behaviors of poly(ethylene terephthalate) (PET) with respect to injection molding were investigated using a differential scanning calorimeter, a haze meter, a polarizing microscope and a small angle light scattering apparatus.
Due to slow crystallization rate of PET, the temperature range between the glass transition temperature and the peak temperature (Tcl) of crystallization from glassy state is wider than those of PBT, PA6 and other semicrystalline polymers. The temperature range is one of the important factors governing the moldability of PET. It was found that Tcl of PET can be controlled by co-polymerization or alloying with specific miscible polymers. By cold crystallization, the modified PET compositions generate spherulitic microstructures. For reinforced PET, lowering the value of Tcl is effective in obtaining high crystallinity in the article molded even at low mold temperatures and then for improving moldability. For transparent applications, raising the value of Tcl by either increasing molecular weight or co-polymerization is effective in enlarging the range of molding conditions and then improving moldability.
Key words: Poly(ethylene terephthalate), cold
crystallization temperature, injection molding, moldability, spherulite